What is a complete protein?
Protein is made up of smaller molecules called amino acids, which are the building blocks for muscles, hormones, and body tissues. There are 20 total amino acids, but nine of these, known as essential amino acids (EAAs), cannot be produced by the human body. A food is considered a “complete protein” if it contains sufficient amounts of all nine of these essential amino acids.
For decades, animal products like meat, eggs, and dairy were considered the gold standard for complete proteins, leading to concerns that plant-based diets were inherently lacking. However, as dietary science has evolved, researchers have proven that it is possible to acquire all necessary amino acids by eating a variety of plant foods. For those seeking a convenient, single-source complete protein, the options are more limited, and this is where pistachios stand out.
Pistachios: The Nut with a Complete Protein Profile
According to new research, roasted American pistachios have been classified as a complete protein for individuals over five years old. This means they provide all nine essential amino acids in adequate amounts to be easily utilized by the body. This is a significant finding, as most other nuts are considered "incomplete" proteins due to having lower amounts of one or more essential amino acids, most commonly lysine.
More than just protein
Pistachios offer much more than just a complete protein profile. Per one-ounce serving, they provide 6 grams of protein, along with a host of other nutrients. They are also high in fiber, antioxidants, healthy fats, potassium, and vitamin B6. The combination of protein and fiber helps increase feelings of fullness, making them an excellent snack for weight management. The antioxidants, including lutein and zeaxanthin, are beneficial for eye health. Their overall nutritional density makes them a smart addition to any diet, especially plant-based ones.
Complementary Proteins: The Key to Balanced Plant Diets
For those who don't rely on pistachios, it's important to understand the concept of complementary proteins. Many plant foods have different amino acid profiles. By combining them, either in the same meal or throughout the day, you can get all nine essential amino acids. For example, legumes are often rich in lysine but low in methionine, while grains are the opposite. Pairing them (e.g., rice and beans) creates a complete protein profile. The American Pistachio Growers website offers further insights into the benefits of pistachios and other plant proteins for health.
Common Combinations for a Complete Protein:
- Legumes (beans, lentils) with Grains (rice, wheat)
- Nuts (like almonds) with Seeds (like sesame seeds)
- Hummus and whole-wheat pita
- Peanut butter on whole-grain toast
Comparison of Amino Acid Profiles in Popular Nuts
While only pistachios are a complete protein among tree nuts, others still offer valuable protein and a wide range of nutrients. The following table provides a comparison based on available nutritional data.
| Nut | Protein per 100g | Amino Acid Profile | Notable Nutrients |
|---|---|---|---|
| Pistachios | 19.4-22.1g | Complete (all 9 EAAs) | Vitamin B6, Potassium, Antioxidants, Fiber |
| Almonds | 16.8-25.4g | Incomplete (often limited in Lysine) | Vitamin E, Magnesium, Fiber |
| Peanuts | ~25.8g | Incomplete (often limited in Methionine/Cysteine) | High Protein, Biotin, Resveratrol |
| Walnuts | 14.4-16.0g | Incomplete (higher in some EAAs, but not complete) | Omega-3 fatty acids, Antioxidants |
Conclusion
For those seeking a straightforward answer to 'What nuts have all 9 amino acids?', the pistachio is the clear winner, holding the unique status of a complete plant-based protein among tree nuts. However, the broader lesson in plant-based nutrition is that single-food completeness isn't necessary. A varied diet that includes different plant protein sources, from nuts and seeds to legumes and grains, will naturally provide all the essential amino acids your body needs. Incorporating a handful of pistachios, or a mix of various nuts and seeds, is a simple and delicious way to ensure you are meeting your protein goals while reaping the benefits of a nutrient-dense food.
Other Plant-Based Complete Protein Sources
Beyond nuts, there are other readily available plant-based sources of complete protein:
- Quinoa: A gluten-free grain that provides all nine essential amino acids.
- Soybeans: Including tofu and edamame, soybeans are a well-known complete protein source.
- Hemp Seeds: These seeds are an excellent source of omega-3s and all essential amino acids.
- Chia Seeds: A complete protein also packed with fiber and omega-3s.
